The invention relates to a belt retractor comprising a belt tensioner and a force-limiting device, wherein the belt tensioner includes a pivoted pinion gear associated with a belt reel, a drive unit and an oblong force-transmitting element movable by the drive unit which is at least partly supported in a tubular portion and can be engaged in the pinion gear so as to rotate the pinion gear in a tensioning direction.
Belt retractors usually include a belt tensioner adapted to counteract a belt slack of the seat belt and a film-spool effect of the seat belt wound on the belt reel. Such belt tensioner comprises, e.g., a pivoted pinion gear coupled to the belt reel, a drive unit and a force-transmitting element moved by the drive unit which is at least partly supported in a tubular portion, the tubular portion usually being curved for lack of space. Upon activation of the belt tensioner the force-transmitting element is displaced in the tubular portion and partly driven out of the same by the, for example, pyrotechnic drive unit. The force-transmitting element then engages in the pinion gear and with a further movement causes a rotation of the pinion gear and thus of the belt reel coupled to the pinion gear in a tensioning direction. The force-transmitting element is designed so that the force-transmitting element is in mesh with the pinion gear in the position taken by the pinion gear after rotation by the force-transmitting element.
Upon completion of the tensioning operation a force-limiting device ensures that the restraining force of the seat belt acting on the vehicle occupant after tensioning does not excessively increase during the vehicle deceleration. For this purpose, upon completion of the tensioning operation a defined webbing extension is allowed by the force limiter permitting a limited rotation of the belt reel in the direction of webbing extension, i.e. against the tensioning direction. By rotation of the belt reel also the pinion gear coupled to the belt reel is rotated against the tensioning direction, however, whereby the force-transmitting element which continues engaging in the pinion gear is pushed back into the tubular portion. Since said tubular portion is curved, however, the force-transmitting element has to be additionally bent during insertion so as to adapt the force-transmitting element to the course of the tubular portion again. To this end, an additional deformation has to take place which results in an increase in the compressive force required for inserting the force-transmitting element. However, this affects the responsive behavior of the force-limiting device, as in the case of force limitation this compressive force has to be overcome in addition to the resistance of the force limiter.